1. Technical Field
The present invention relates to a control apparatus for a damping force varying damper and a damping force varying damper system.
2. Related Art
A suspension apparatus of a vehicle such as an automobile includes a damper in order to appropriately reduce vibration transmitted from a road surface to a vehicle body during traveling to improve riding comfort and steering stability. The damper is provided with, for example, a partitioning member movably installed in a cylinder to partition the inside of the cylinder, a rod member connected to the partitioning member, and a liquid storage chamber that compensates for an amount of oil corresponding to the volume of the rod member in conjunction with movement of the rod member. The damper offers resistance to a flow of a liquid resulting from movement of the partitioning member to generate a damping force.
At this time, a change in the cross-sectional area of a channel through which the liquid flows changes the resistance of the flow of the liquid, enabling a change in damping force. Thus, a damping force varying damper has recently been proposed which utilizes the above-described phenomenon to allow the damping force to be varied.
For example, Patent Literature 1 (JP-A-2009-23377) describes a control apparatus for a damping force varying damper. In the control apparatus, a target current generating section searches for or sets a first upper limit current value corresponding to the amount of power generated by an alternator and then searches for or sets a second upper limit current value corresponding to a coil temperature. The target current generating section then selects a smaller one of the first and second upper limit current values as an upper limit current value. Then, when a basic target current exceeds the upper limit current value, the target current generating section sets the upper limit target value to be a target current and outputs a driving current according to the target current to an MLV coil in each damper.
To change the cross-sectional area of the channel, for example, a valve disc or the like may be provided in the channel and moved using a solenoid valve. The movement of the valve disc can be controlled by controlling a current passed through the solenoid valve.
However, when a large current is continuously passed through the solenoid valve, the coil, which is a component of the solenoid valve, is excessively heated and is likely to be short-circuited. Furthermore, durability of the coil is likely to be degraded.